At present, high-performance road sports cars are normally rear-drive, and have a self-locking differential for increasing the drive torque transmitted by the rear wheels to the road surface.
Tests have shown, however, that currently marketed self-locking differentials do not always succeed in maximizing the drive torque transmitted by the rear wheels to the road surface. What is more, the presence of the self-locking differential makes the vehicle harder and less safe to drive, in that, should one of the rear wheels temporarily lose grip, the self-locking differential almost immediately transfers part of the drive torque to the other rear wheel, thus possibly resulting in rear-end swerving of the vehicle, which must be skilfully counteracted by the driver acting promptly on the vehicle controls to prevent the vehicle spinning.
U.S. Pat. No. 4,741,407 discloses a system for controlling limited-slip differential gear unit for automotive vehicle. The control system for the limited-slip differential gear unit is associated with a suspension control system to receive therefrom a suspension mode indicative signal to select one of a plurality of preset characteristics to derive a slip-limit control signal; the limited-slip differential gear unit includes a slip-limit adjusting mechanism which is responsive to the control signal for adjusting the slip-limitation to be generated by the limited-slip differential gear unit.
U.S. Pat. No. 5,152,362 discloses a driving torque distribution control system for vehicle; the control system comprises a clutch for limiting a differential action between left and right drive wheels or varying a driving torque distribution between front and rear axles of a 4WD vehicle, a sensor group, and a controller for controlling an engagement force of the clutch to control the differential limiting force or the torque distribution between the front and rear drive wheels. The sensor group includes an accelerator position sensor and a lateral acceleration sensor; the controller increases the clutch engagement force as the speed of increase of the accelerator opening degree increases, and increases the rate of increase of the clutch engagement force with respect to the increasing speed of the accelerator opening degree when the lateral acceleration increases.